Chronic and persistent inflammation is a major cause for the pathogenesis and progression of systemic autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). RA is a highly inflammatory polyarthritis often leading to joint destruction, deformity and loss of function. Additive, symmetric swelling of peripheral joints is the hallmark of the disease. Extra-articular features and systemic symptoms can commonly occur and may antedate the onset of joint symptoms. Chronic pain, disability and excess mortality are unfortunate sequelae. During progression of RA, the synovial lining layer of the inflamed joints increases its thickness as a result of synovial hyperplasia and infiltration into synovial stroma by CD4+ T cells, B cells, CD8+ T cells, macrophages, dendritic cells and neutrophils (Feldmann, M. et al., Cell, 85:307-10 (1996); Moreland, L. W. et al., N Engl J Med, 337:141-7 (1997)). In SLE, the production of autoantibodies results in the deposition of immune complex in many tissues and organs including glomeruli, skin, lungs and synovium, thereby generating rheumatic lesions with characteristic chronic inflammation and tissue damage.
In several arthritis models, depletion of neutrophils resulted in a decrease of arthritis severity. The most common animal model for RA is collagen-induced arthritis (CIA) in which challenge with type II chicken collagen (CII) induces persistent chronic inflammation in all major joints of DBA/1j mice (Williams, R. O., et al., Proc Natl Acad Sci USA, 91:2762-6 (1994)). While CD4+ T cells have long been considered to play a central role in the pathogenesis of RA, there is renewed interest in addressing the pivotal role of neutrophils in initiation, progression and maintenance of RA. Massive infiltration of neutrophils in the lesions releases the proinflammatory cytokines including TNF-α, IL-1 and IL-6, which can affect the functions of neutrophils and other inflammatory cells.
An extensively studied murine model for SLE is the lpr strain, in which mutation of Fas apoptotic gene leads to spontaneous autoimmune disorders similar to human SLE. Studies in this strain recapitulate many aspects of human SLE symptoms. For example, lpr mice develop anti-chromatin, anti-DNA, and anti-IgG serum autoantibodies as well as a polyclonal increase of total immunoglobulin. Disease severity is highly dependent on genetic background. For example, MRL-lpr/lpr mice produce high levels of IgG autoantibodies to DNA and develop a severe glomerulonephritis due to deposition of immune complexes, while C57BL/6(B6)-lpr/lpr mice produce low level autoantibodies with much mild immunopathology.
Co-signal molecules, including those with costimulatory and coinhibitory functions, are important for the induction of effective immune response and for the prevention of unwanted autoimmunity. It has been shown that signals through the B7-CD28 family are major regulators of this balance and play a pivotal role in the regulation of autoimmunity. Persistence of inflammatory responses in systemic autoimmune diseases implies either an impaired coinhibitory or enhanced costimulatory functions, leading to the loss of the balance. In this regard, it is particularly interesting that autoantibodies against B7-H1, a primary coinhibitory molecule after binding to its receptor PD-1, is found in a significant proportion of RA patients and the presence of the autoantibodies is implicated in the progression of RA symptoms.
Soluble forms of B7-CD28 family molecules are also implicated in the progression of rheumatoid diseases. A recent study shows that soluble PD-1 could be detected in RA patients and the levels of soluble PD-1 are correlated with TNF-alpha concentration in synovial fluid. B7-H4 is a more recent addition to the B7 family member. B7-H4 has potent inhibitory effects on T cells through binding to a putative receptor. Cell surface B7-H4 is normally not detectable in normal tissues, although its surface expression could be upregulated on macrophages and tumor cells by inflammatory cytokines, including IL-10 and IL-6. It has been reported that B7-H4 could suppress T cell response in the presence of antigen stimulation. Soluble B7-H4 (sH4) has also been detected in ovarian cancer patients as a potential biomarker, but the mechanism of production and the function of sH4 is unknown. B7-H4 deficient mice were found to mount slightly enhanced T helper 1 type T cell responses against Leishmania major infection. Using independently generated B7-H4 knockout mice, it was demonstrated that the lack of B7-H4 led to resistance to Listeria monocytogenes infection occurs by direct regulation of growth of neutrophil progenitors. Methods and devices for detecting and quantifying sH4 are needed to explore the role sH4 plays in inflammatory disorders including autoimmune disorders.
It is an object of the invention to provide methods and devices for detecting or quantifying levels of sH4 in a subject.
It is another object of the invention to provide methods and devices for determining the stage or progression of an inflammatory disorder in a subject.
It is still another object of the invention to provide methods and devices to diagnose or to assist in the diagnosis of an inflammatory disorder.